Method of supporting signal transmission and reception using at least two radio access technologies and apparatus therefor

ABSTRACT

A method of supporting communication using two or more heterogeneous radio access technologies (RAT) comprises: receiving a setup message providing instructions for access to a second base station in a second communication network supporting the second RAT from a first base station in a first communication network supporting a first RAT; and attempting to access the second base station. At this time, when the terminal successfully accesses the second base station, specific traffic type data are transmitted and received through the second base station, and data other than the specific traffic type can be transmitted and received through the first base station.

TECHNICAL FIELD

The present invention relates to a wireless communication, and moreparticularly, to a method of supporting signal transmission andreception using at least two radio access technologies (RATs) andapparatus therefor.

BACKGROUND ART

There may exist a multi-RAT user equipment having capability ofaccessing at least two radio access technologies (RATs). In order toaccess a specific radio access technology (hereinafter abbreviated RAT),a connection to the specific RAT is established on the basis of a userequipment request and data transmission and reception may be thenperformed. Yet, even if the multi-RAT user equipment is capable ofaccessing at least two RATs, it is unable to access a plurality of RATsat the same time. In particular, currently, even if a user equipment hasmulti-RAT capability, it is unable to simultaneously perform datatransmission/reception through different RATs.

The above-mentioned multi-RAT technology of the related art is aswitching based multi-RAT technology. Since all transmitted data aretransmitted in a manner of being switched to another RAT, the relatedart multi-RAT technology has a problem in selecting an RAT suitable forcharacteristics of a flow. However, a solution for this problem has notbeen proposed yet.

DISCLOSURE OF THE INVENTION Technical Tasks

One technical task intended to achieve by the present invention is toprovide a method for a user equipment to support a signal transmissionand reception using two or more radio access technologies (RATs).

Another technical task intended to achieve by the present invention isto provide a method for a base station to support a signal transmissionand reception using two or more radio access technologies (RATs).

Another technical task intended to achieve by the present invention isto provide a user equipment supporting a signal transmission andreception using two or more radio access technologies (RATs).

The other technical task intended to achieve by the present invention isto provide a base station supporting a signal transmission and receptionusing two or more radio access technologies (RATs).

Technical tasks obtainable from the present invention are non-limitedthe above mentioned technical tasks. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of supporting signal transmission andreception using two or more radio access technologies (RATs), which issupported by a user equipment can include the steps of

receiving a setup message indicating access to a second base station ofa second communication network supporting a second RAT from a first basestation of a first communication network supporting a first RAT andattempting to access the second base station. In this case, if theaccess to the second base station is successfully performed, data on aspecific traffic type is transmitted and received via the second basestation and data except the data on the specific traffic type may betransmitted and received via the first base station.

The setup message may include flow information indicating the specifictraffic type, which is to be transmitted and received via the secondbase station.

Additionally, the setup message may include action time informationindicating a timing of communicating with the second base station. Ifthe setup message includes the action time information, the userequipment may begin to transceive data with the second base station on atiming indicated by the action time information.

The method of supporting signal transmission and reception using two ormore radio access technologies (RATs), which is supported by the userequipment, may further include the step of transmitting a completionmessage, which is used to report whether the access to the second basestation is successful, to the first base station.

In this case, the completion message may be transmitted only when theuser equipment successfully accesses the second base station.

The completion message may include a status value indicating whether theaccess to the second base station is successful.

Additionally, the completion message may include an address valuereceived from the second base station by the user equipment.

If the access to the second base station fails, the method of supportingsignal transmission and reception using two or more radio accesstechnologies (RATs), which is supported by the user equipment, mayfurther include the step of receiving the setup message indicating anaccess to a new second base station from the first base station again.

If the second base station of a predetermined condition is searched, themethod of supporting signal transmission and reception using two or moreradio access technologies (RATs), which is supported by the userequipment, may further include the step of transmitting a requestmessage requesting an access to the second base station to the firstbase station.

In this case, if the user equipment detects a second base stationpreferred by the user equipment, the predetermined condition detects thepreferred second base station and the predetermined condition may beconfigured by at least one of a case that a measurement result for thepreferred second base station is higher than a threshold and a case thata measurement result for the second base station is higher than ameasurement result for the first base station.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, amethod of supporting signal transmission and reception using two or moreradio access technologies (RATs), which is supported by a first basestation of a first communication network supporting a first RAT,includes the steps of transmitting a setup message indicating access toa second base station of a second communication network supporting asecond RAT to a user equipment supporting the two or more RATs andreceiving a completion message, which is used to report whether theaccess to the second base station is successful, from the userequipment. In this case, if the user equipment successfully accesses thesecond base station, data on a specific traffic type among data to betransmitted to the user equipment changes a transmission path to thesecond base station and data except the data on the specific traffictype are directly transmitted to the user equipment.

The setup message may include flow information indicating the specifictraffic type, which is to be transmitted and received via the secondbase station.

Additionally, the setup message may include action time informationindicating a communication timing between the user equipment and thesecond base station. If the setup message includes the action timeinformation, the first base station may change the transmission path ofthe data on the specific traffic type to the second base station on atiming indicated by the action time information.

If the user equipment fails to access the second base station, themethod of supporting signal transmission and reception using two or moreradio access technologies (RATs), which is supported by a first basestation of a first communication network supporting a first RAT, mayfurther include the step of retransmitting the setup message indicatingaccess to a new second base station to the user equipment.

In this case, if the completion message is not received until a timer,which is started after the setup message is transmitted, elapses, thefirst base station may determine that access establishment between theuser equipment and the second base station fails.

As a different example, the first base station may determine whether theaccess establishment is successful via a status value included in thecompletion message indicating whether the user equipment succeeds inaccessing the second base station.

The completion message includes an address value received from thesecond base station by the user equipment and the first base station maychange the transmission path of the data on the specific traffic typebased on the address value.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, a user equipment supporting signal transmission andreception using two or more radio access technologies (RATs) may includea communication unit and a processor, the processor configured tocontrol the communication unit to receive a setup message indicatingaccess to a second base station of a second communication networksupporting a second RAT from a first base station of a firstcommunication network supporting a first RAT, the processor configuredto control the communication unit to attempt to access the second basestation. If the access to the second base station is successfullyperformed, data on a specific traffic type is transmitted and receivedvia the second base station and data except the data on the specifictraffic type may be controlled to be transmitted and received via thefirst base station.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, a base station of a first communication network supporting afirst RAT, which supports signal transmission and reception using two ormore radio access technologies (RATs), may include a communication unitand a processor, the processor configured to control the communicationunit to transmit a setup message indicating access to a second basestation of a second communication network supporting a second RAT to auser equipment supporting the two or more RATs, the processor configuredto control the communication unit to receive a completion message, whichis used to report whether the access to the second base station issuccessful, from the user equipment. If the user equipment successfullyaccesses the second base station, data on a specific traffic type amongdata to be transmitted to the user equipment changes a transmission pathto the second base station and data except the data on the specifictraffic type may be controlled to be directly transmitted to the userequipment.

Advantageous Effects

According to various embodiments of the present invention, a userequipment supporting both a cellular and a WLAN may efficiently performselection of a heterogeneous network for a flow via a control of acellular network in a wideband wireless communication system.

According to various embodiments of the present invention, a multi-RATaccess method of a non-switching scheme may be provided in a widebandwireless communication system.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects may be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. The above and other aspects, features, and advantages of thepresent invention will become more apparent upon consideration of thefollowing description of preferred embodiments, taken in conjunctionwith the accompanying drawing figures. In the drawings:

FIG. 1 is a block diagram for configurations of a base station 105 and auser equipment 110 in a wireless communication system 100;

FIG. 2 is a diagram for one example of a network structure to describean interoperating structure of a first communication system (e.g., LTEsystem) and a second communication system (e.g., WiFi system);

FIG. 3A and FIG. 3B are diagrams for examples to describe scenariosaccording to the present invention;

FIG. 4 is a diagram for one example to describe a multi-systemcapability related negotiation procedure according to the presentinvention;

FIG. 5 is a diagram for one example to describe traffic characteristicsin LTE system;

FIG. 6 is a diagram to describe a system selecting method using QoSclass defined in LTE;

FIG. 7 is a diagram for one example to describe a measurement gap in LTEsystem;

FIG. 8 is a flowchart of a process for a UE to report a measurementresult to an eNB;

FIG. 9 is a diagram for one example to describe a measurement object anda report configuration for a measurement result;

FIG. 10 is a diagram of enumerated trigger conditions;

FIG. 11 is a flowchart to describe a message defined for a secondarysystem management procedure;

FIG. 12 is a flowchart to describe an additional procedure of asecondary system;

FIG. 13 is a flowchart to describe a changing procedure of a secondarysystem; and

FIGS. 14A to 14C are flowcharts to describe a deleting procedure of asecondary system.

BEST MODE Mode for Invention

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. In the following detailed description of the inventionincludes details to help the full understanding of the presentinvention. Yet, it is apparent to those skilled in the art that thepresent invention may be implemented without these details. Forinstance, although the following descriptions are made in detail on theassumption that a mobile communication system includes 3GPP LTE/LTE-Asystem, the following descriptions are applicable to other random mobilecommunication systems in a manner of excluding unique features of the3GPP LTE/LTE-A.

Occasionally, to prevent the present invention from getting vaguer,structures and/or devices known to the public are skipped or may berepresented as block diagrams centering on the core functions of thestructures and/or devices. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Besides, in the following description, assume that a terminal is acommon name of such a mobile or fixed user stage device as a userequipment (UE), a mobile station (MS), an advanced mobile station (AMS)and the like. And, assume that a base station (BS) is a common name ofsuch a random node of a network stage communicating with a terminal as aNode B (NB), an eNode B (eNB), an access point (AP) and the like.Although the present specification is described based on IEEE 802.16system, contents of the present invention may be applicable to variouskinds of other communication systems.

In a mobile communication system, a user equipment is able to receiveinformation in downlink and is able to transmit information in uplink aswell. Informations transmitted or received by the user equipment nodemay include various kinds of data and control informations. Inaccordance with types and usages of the informations transmitted orreceived by the user equipment, various physical channels may exist.

The following descriptions are usable for various wireless accesssystems including CDMA (code division multiple access), FDMA (frequencydivision multiple access), TDMA (time division multiple access), OFDMA(orthogonal frequency division multiple access), SC-FDMA (single carrierfrequency division multiple access) and the like. CDMA may beimplemented by such a radio technology as UTRA (universal terrestrialradio access), CDMA 2000 and the like. TDMA may be implemented with sucha radio technology as GSM/GPRS/EDGE (Global System for Mobilecommunications)/General Packet Radio Service/Enhanced Data Rates for GSMEvolution). OFDMA may be implemented with such a radio technology asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, E-UTRA (EvolvedUTRA), etc. UTRA is a part of UMTS (Universal Mobile TelecommunicationsSystem). 3GPP (3rd Generation Partnership Project) LTE (long termevolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA. The 3GPPLTE adopts OFDMA in DL and SC-FDMA in UL. And, LTE-A (LTE-Advanced) isan evolved version of 3GPP LTE.

Moreover, in the following description, specific terminologies areprovided to help the understanding of the present invention. And, theuse of the specific terminology may be modified into another form withinthe scope of the technical idea of the present invention.

FIG. 1 is a block diagram for configurations of a base station 105 and auser equipment 110 in a wireless communication system 100.

Although one base station 105 and one user equipment 110 (D2D userequipment included) are shown in the drawing to schematically representa wireless communication system 100, the wireless communication system100 may include at least one base station and/or at least one userequipment.

Referring to FIG. 1, a base station 105 may include a transmitted (Tx)data processor 115, a symbol modulator 120, a transmitter 125, atransceiving antenna 130, a processor 180, a memory 185, a receiver 190,a symbol demodulator 195 and a received (Rx) data processor 197. And, auser equipment 110 may include a transmitted (Tx) data processor 165, asymbol modulator 170, a transmitter 175, a transceiving antenna 135, aprocessor 155, a memory 160, a receiver 140, a symbol demodulator 155and a received (Rx) data processor 150. Although the base station/userequipment 105/110 includes one antenna 130/135 in the drawing, each ofthe base station 105 and the user equipment 110 includes a plurality ofantennas. Therefore, each of the base station 105 and the user equipment110 of the present invention supports an MIMO (multiple input multipleoutput) system. And, the base station 105 according to the presentinvention may support both SU-MIMO (single user-MIMO) and MU-MIMO (multiuser-MIMO) systems.

In downlink, the transmitted data processor 115 receives traffic data,codes the received traffic data by formatting the received traffic data,interleaves the coded traffic data, modulates (or symbol maps) theinterleaved data, and then provides modulated symbols (data symbols).The symbol modulator 120 provides a stream of symbols by receiving andprocessing the data symbols and pilot symbols.

The symbol modulator 120 multiplexes the data and pilot symbols togetherand then transmits the multiplexed symbols to the transmitter 125. Indoing so, each of the transmitted symbols may include the data symbol,the pilot symbol or a signal value of zero. In each symbol duration,pilot symbols may be contiguously transmitted. In doing so, the pilotsymbols may include symbols of frequency division multiplexing (FDM),orthogonal frequency division multiplexing (OFDM), or code divisionmultiplexing (CDM).

The transmitter 125 receives the stream of the symbols, converts thereceived stream to at least one or more analog signals, additionallyadjusts the analog signals (e.g., amplification, filtering, frequencyupconverting), and then generates a downlink signal suitable for atransmission on a radio channel. Subsequently, the downlink signal istransmitted to the user equipment via the antenna 130.

In the configuration of the user equipment 110, the receiving antenna135 receives the downlink signal from the base station and then providesthe received signal to the receiver 140. The receiver 140 adjusts thereceived signal (e.g., filtering, amplification and frequencydownconverting), digitizes the adjusted signal, and then obtainssamples. The symbol demodulator 145 demodulates the received pilotsymbols and then provides them to the processor 155 for channelestimation.

The symbol demodulator 145 receives a frequency response estimated valuefor downlink from the processor 155, performs data demodulation on thereceived data symbols, obtains data symbol estimated values (i.e.,estimated values of the transmitted data symbols), and then provides thedata symbols estimated values to the received (Rx) data processor 150.The received data processor 150 reconstructs the transmitted trafficdata by performing demodulation (i.e., symbol demapping, deinterleavingand decoding) on the data symbol estimated values.

The processing by the symbol demodulator 145 and the processing by thereceived data processor 150 are complementary to the processing by thesymbol modulator 120 and the processing by the transmitted dataprocessor 115 in the base station 105, respectively.

In the user equipment 110 in uplink, the transmitted data processor 165processes the traffic data and then provides data symbols. The symbolmodulator 170 receives the data symbols, multiplexes the received datasymbols, performs modulation on the multiplexed symbols, and thenprovides a stream of the symbols to the transmitter 175. The transmitter175 receives the stream of the symbols, processes the received stream,and generates an uplink signal. This uplink signal is then transmittedto the base station 105 via the antenna 135.

In the base station 105, the uplink signal is received from the userequipment 110 via the antenna 130. The receiver 190 processes thereceived uplink signal and then obtains samples. Subsequently, thesymbol demodulator 195 processes the samples and then provides pilotsymbols received in uplink and a data symbol estimated value. Thereceived data processor 197 processes the data symbol estimated valueand then reconstructs the traffic data transmitted from the userequipment 110.

The processor 155/180 of the user equipment/base station 110/105 directsoperations (e.g., control, adjustment, management, etc.) of the userequipment/base station 110/105. The processor 155/180 may be connectedto the memory unit 160/185 configured to store program codes and data.The memory 160/185 is connected to the processor 155/180 to storeoperating systems, applications and general files.

The processor 155/180 may be called one of a controller, amicrocontroller, a microprocessor, a microcomputer and the like. And,the processor 155/180 may be implemented using hardware, firmware,software and/or any combinations thereof. In the implementation byhardware, the processor 155/180 may be provided with one of ASICs(application specific integrated circuits), DSPs (digital signalprocessors), DSPDs (digital signal processing devices), PLDs(programmable logic devices), FPGAs (field programmable gate arrays),and the like.

Meanwhile, in case of implementing the embodiments of the presentinvention using firmware or software, the firmware or software may beconfigured to include modules, procedures, and/or functions forperforming the above-explained functions or operations of the presentinvention. And, the firmware or software configured to implement thepresent invention is loaded in the processor 155/180 or saved in thememory 160/185 to be driven by the processor 155/180.

Layers of a radio protocol between a user equipment and an base stationmay be classified into first layer L1, second layer L2 and third layerL3 based on 3 lower layers of OSI (open system interconnection) modelwell known to communication systems. A physical layer belongs to thefirst layer and provides an information transfer service via a physicalchannel. RRC (radio resource control) layer belongs to the third layerand provides control radio resourced between UE and network. A userequipment and a base station may be able to exchange RRC messages witheach other via radio communication layer and RRC layers.

In the present specification, the processor 155 of the user equipment110 performs operations of processing signals and data except a signaltransceiving function of the user equipment 110 and a storing functionof the user equipment 110. And, the processor 180 of the base station105 performs operations of processing signals and data except a signaltransceiving function of the user equipment 110 and a storing functionof the user equipment 110. Yet, for clarity of the followingdescription, the processors 155 and 180 shall not be mentioned overall.Although the processor 155/180 is not mentioned specially, the processor155/180 may be regarded as performing a series of operations includingdata processing and the like except a signal transceiving function and astoring function.

The present invention proposes a method for a user equipment, whichsupports both a cellular network and a wireless LAN network (e.g., WLAN)in a broadband wireless communication system, to efficiently perform aheterogeneous network selection for a flow through a control of thecellular network.

FIG. 2 is a diagram for one example of a network structure to describean interoperating structure of a first communication system (e.g., LTEsystem) and a second communication system (e.g., WiFi system).

In the network structure shown in FIG. 2, a backhaul control connectionis established between an AP and an eNB through a backbone network(e.g., P-GW, EPC (evolved packet core), etc.) or a wireless controlconnection may be established between the AP and the eNB. For peakthroughput and data traffic off-loading, a user equipment (hereinafterabbreviated UE) is able to support both a first communication system (ora first communication network) using a first wireless communicationscheme and a second communication system (or a second communicationnetwork) using a second communication scheme through interoperationsamong a plurality of communication networks. In this case, the firstcommunication network and the first communication system may be named aprimary network and a primary system, respectively. The secondcommunication network and the second communication system may be named asecondary network and a secondary communication system, respectively.For instance, the UE may be configured to simultaneously support LTE (orLTE-A) and WiFi (e.g., a short range communication system such as WLAN,802.11, etc.). Such a UE may be named a multi-system capability UE inthe present specification.

In the network structure shown in FIG. 2, the primary system has a widercoverage and may include a network for control information transmission.For example, the primary system may include one of WiMAX system, LTEsystem and the like. On the other hand, the secondary system is anetwork having a smaller coverage and may include a system for datatransmission. For example, the secondary network may include a wirelessLAN system such as WLAN, WiFi and the like.

FIG. 3A and FIG. 3B are diagrams for examples to describe scenariosaccording to the present invention.

FIG. 3A shows a first scenario having a backhaul control connectionestablished between an AP and an eNB (i.e., a base station) via abackbone network. And, FIG. 3B shows a second scenario capable of adirect communication owing to a wireless control connection establishedbetween an AP and an eNB. In aspect of the eNB in each of the scenarios,the AP of a secondary system may look like an entity operating in amanner identical to that of a UE having LTE capability.

In the following description, definitions related to a multi-RAT systemof the present invention are explained.

Primary System

A primary system (e.g., WiMAX, LTE network, etc.) is a system having awider coverage. And, the primary system means a network in a connectedstate in a network having a constant status (or RRC connection) with amulti-system capability UE or a network in a DRX (discontinuousreception) or idle status.

A multi-system capability UE may send an indication, which indicatesthat the multi-system capability UE has capability for a heterogeneousnetwork (e.g., WLAN, etc.), to an eNB of a primary system during aconnection establishment with a primary network. In this case, theindication of the multi-system capability may be transmitted in a mannerof being included as a new field in RRCConnectionRequest orRRCConnectionSetup message. If the indication of the multi-systemcapability is set to 1, a UE and an eNB may share capability necessaryfor a multi-system through a specific procedure for the multi-systemcapability UE.

An eNB of a primary system may periodically transmit information onanother system (secondary systems) belonging to the same coverage formulti-system UEs using a broadcast message or a unicast message. Ifdeployment of a secondary system is changed, it is able to send anupdated message to indicate added/deleted/changed information of thesecondary system.

Secondary System

A secondary system is a system having a small coverage and may includeone of WLAN system, WiFi system and the like for example. The secondarysystem is the system that may be added or deleted if necessary. Thesecondary system may be mainly used for data transmission and receptionthat requires higher bandwidth (BW). In doing so, a specific flow (QoS)may be mapped.

A connection or release between a secondary system and a UE is possibleafter confirmation from a primary system. In this case, the connectionbetween a secondary system and a UE may mean that it is ready totransmit/receive data or that data is transmitted/received.

If it is detected that a UE has entered a secondary system coverage,information on an access to a secondary system may be received through aprimary system. In doing so, actual data transmission/reception may notoccur instantly.

If a UE has data to transmit/receive via a secondary system, it is ableto receive access information on a corresponding flow through a primarysystem. In doing so, actual data transmission/reception may occurinstantly.

FIG. 4 is a diagram for one example to describe a multi-systemcapability related negotiation procedure according to the presentinvention.

FIG. 4 is provided for UE capability negotiation on the basis of LTE andshows a process for an eNB, which has capability for a heterogeneousnetwork interoperating technology such as a wireless LAN, to receive aheterogeneous network related information of a UE by sendingUECapabilityEnquiry message to the UE.

Referring to FIG. 4, a UE (i.e., a multi-system capability UE) performsan initial network entry procedure with a primary system (i.e., an eNBof the primary system) [S410]. In particular, the UE performs an initialconnection establishment with the primary system. In case that theprimary system includes an LTE system, the UE performs an initial RRC(radio resource control) connection establishment of the previous LTE.In the initial network entry procedure, the corresponding UE may informa base station that the corresponding UE is the multi-system ormulti-RAT capability UE. For instance, the UE may send the correspondingindication to the base station through RRCConnectionRequest message orin the course of RRCConnectionSetup procedure. In particular, such aparameter (e.g., 1-bit size) as ‘MultiRATAccessAvaialble’ may betransmitted in a manner of being added to the RRCConnectionRequestmessage or the RRCConnectionSetup procedure.

If there is a common information, which should be received by the UE, ofa base station (hereinafter called an AP (access point)) of a secondarysystem, a base station (hereinafter called an eNB) of the primary systemmay transmit an information on the secondary system to the UE [S420].

On the other hand, unlike the description of the step S410 withreference to FIG. 4, the multi-system (or multi-RAT) capabilitynegotiation may be performed after the initial connection establishment.

In case of a connection reestablishment, the multi-system (or multi-RAT)capability negotiation may be skipped. In case of a handover, a targeteNB may perform a pre-negotiation through a backbone network from aserving eNB. After the UE has entered RRC-IDLE state, the eNB may storethe multi-system capability of the UE for predetermined duration. If anetwork reconfiguration is performed before multi-system informationretain timeout, the negotiation may be omitted.

The eNB may send a message, which queries the capability of the UE(e.g., whether the UE is capable of accessing the multi-system or themulti-RAT simultaneously, whether the UE is capable to simultaneouslyaccessing a prescribed system and a prescribed RAT, etc.), to the UE[S430]. This message may be named ‘UECapabilityEnquiry’. As aUE-CapabilityRequest parameter is added to the UECapabilityEnquirymessage, the UECapabilityEnquiry is sent with a content of the addedparameter to query whether the UE is capable of supporting themulti-system or the multi-RAT simultaneously or whether the UE iscapable of supporting a prescribed system. In this case, theUE-CapabilityRequest parameter may be transmitted in a manner ofincluding a parameter about such a new radio access technology (RAT)(i.e., an unlicensed band) as WiFi, WLAN, 802.11 and the like.

In response to the UECapabilityEnquiry message, the UE sends aUECapabilityInformation message to the eNB [S440]. ThisUECapabilityInformation message may contain WiFi related capabilityinformation for example.

The UECapabilityInformation message may include an indicator indicatingcapability of simultaneously accessing a plurality of radio accesstechnologies or system types and information on supportable radio accesstechnologies or system types. For instance, if the supportable ratioaccess technology includes WiFi, the UECapabilityInformation message maycontain 802.11 MAC address (for authentication information) of the UE inaddition. The UECapabilityInformation message may contain a previouslyaccessed AP information (UE's preferred AP). And, the information ispreferably transmitted to the eNB to which the previously accessed APbelongs. And, the UECapabilityInformation message may additionallycontain Protocol Version (11a/b/n . . . ) information and information ona type or characteristic (e.g., EPS bearer QoS type) of a trafficdesired to be transmitted or received via WLAN. This information of thetraffic type or characteristic shall be described in detail later.

Thus, as the UE and the eNB exchange the UECapabilityEnquiry message andthe UECapabilityInformation message with each other, the followingcontent shown in Table 1 needs to be additionally included in theprevious standard specification 3GPP TS 36.331.

TABLE 1 Insert below description to 5.6.3.3 Reception of the UECapability Enquiry by the UE (3GPP TS 36.331) The UE shall: 1> set thecontents of UECapability Information message as follows: 2> if theue-CapabilityRequest includes wifi and if the UE supports WiFi (or WLANor 802.11x) domain: 3>  include the UE radio access capabilities forWiFi within a ue-CapabilityRAT-Container and with the rat-Type set toWiFi(or WLAN or 802.11x); 1> submit the UECapabilityInformation messageto lower layers for transmission, upon which the procedure ends

Having received the supportable radio access technology or system typeinformation through the UECapabilityInformation message, the eNB sendsUECapabilityComplete or UECapabilityResponse message [S450]. In thiscase, the UECapabilityComplete or UECapabilityResponse message maycontain candidate APs information.

In the case shown in FIG. 4, only if a previous UECapabilityEnquirymessage is sent (1 step), the UE sends the UECapabilityInformationmessage (2 step). In this case, the eNB may send theUECapabilityComplete message in response to the UECapabilityInformationmessage (3 step), which is an optional step. Hence, the MultiRATcapability negotiation procedure may include 2 or 3 steps.

Alternatively, the MultiRAT capability negotiation procedure may beconfigured to include 1 or 2 steps. In particular, without a previousUECapabilityEnquiry message, the UECapabilityInformation may be sent tothe eNB in an unsolicited manner under the decision made by the UE (1step). In this case, the eNB may send UECapabilityComplete message tothe UE in response to the UECapabilityInformation message (optional) (2steps).

After the step S450, the UE may exchange data with the eNB [S460]. Basedon the candidate AP list (or APs) received in the step S450, the UE mayselect the AP by performing a secondary system scanning [S470]. Afterthe scanning, the UE may perform a secondary system management [S480].In this case, there is a trigger condition for a secondary system (e.g.,AP) measurement. Prior to describing the definition of the triggercondition, QoS (quality of service) indicating a traffic state isschematically described with reference to 3GPP LTE system for example.

FIG. 5 is a diagram for one example to describe traffic characteristicsin LTE system.

Referring to FIG. 5, if a UE accesses an LTE network, EPS (evolvedpacket system) Bearer is generated from the UE to P-GW (i.e.,UE-eNB-S-GW-P-GW) [GTP type tunnel]. In particular, a plurality of EPSBearers may be generated depending on each service property. Forinstance, Internet EPS Bearer, IPTV EPS Bearer, VoIP EPS Bearer and thelike may be generated. Properties of Default EPS Bearer and DedicatedEPS Bearer are described as follows.

Default EPS Bearer—QoS property of Default EPS Bearer includes Non-GBR(Non-Guaranteed Bit Rate), e.g., Internet service.

Dedicated EPS Bearer—Dedicated EPS Bearer may be generated at GBR orNon-GBR. For instance, Dedicated EPS Bearer for VoD service is generatedat GBR.

LTE QoS is described in brief as follows.

First of all, a previous LTE enables traffic characteristics to bedefined on a network level (i.e., P-GW). In particular, the P-GW defines5-tuple Service Data Flow and an eNB defines GBR or Non-GBR.

PDN connection: IP connection between UE and PDN (UE is identified withIP address, while PDN is identified with APN).

EPS session: Having the same meaning of PDN connection. This session hasat least one EPS bearer. If IP address is assigned to a UE, this sessionis maintained as long as the UE is connected to an IP network.

EPS bearer: A delivery path established between UE and P-GW to transmitIP traffic with specific QoS. Each EPS bearer is configured with QoSparameters indicating property of the delivery path.

Default bearer: This is EPS bearer newly generated when a new PDNconnection is established. This bearer is maintained until the PDNconnection is terminated. This bearer is always configured at non-GBR.

Dedicated Bearer: This is EPS bearer generated on demand additionallyafter PDN connection establishment. Corresponding to GBR or non-GBR.

SDF (Service Data Flow): IP flow corresponding to a service or a set ofIP flows. This flow is identified by an IP of packet and TCP/UDP header.A different QoS is applied per SDF and PCC rules are applied by PCRF.This flow is delivered on EPS bearer that meets QoS of SDF. Several SDFsmay be mapped to the same EPS bearer. User traffic has a different QoSproperty depending on using what kind of service or application. SDF isan IP flow generated from filtering user traffic per service or a set ofIP flows. And, a specific QoS policy is applied in accordance with asubscriber level of UE and a used service. IP flows toward a user aresorted into SDF through SDF template (classifier) in accordance withservice property and are then delivered to a user in a manner of havingQoS policy (e.g., bandwidth control) applied thereto per SDF. On EPSdelivery network, QoS is transmitted in a manner of being mapped to EPSbearer.

EPS bearer: As mentioned in the foregoing description, EPS bearers maybe sorted into a default type and a dedicated type. If a UE accesses anLTE network, an IP address is assigned to the UE. Then, the UEestablishes a PCN connection as soon as EPS bearer is generated. Whilethe UE uses a service (e.g., Internet) through default bearer, if the UEuses another service (e.g., VoD) that cannot be provided through thedefault bearer, dedicated bearer is generated by on-demand. Inparticular, the dedicated bearer is configured by QoS different fromthat of a previously configured bearer. UE may access several APNs. And,one default EPS bearer and sever dedicated EPS bearers may be configuredper APN. Maximum 11 EPS bearers may be configured.

Default bearer is generated when a UE initially accesses a network. Thedefault bearer keeps being maintained even if a service is not used inthe meantime. The default bearer then disappears when the UE leaves thenetwork. One default bearer is generated per PAN. How to generate adefault bearer by applying which QoS to a prescribed APN in case of aninitial access to a network is provisioned as a user's subscriptioninformation in HSS. If a UE initially accesses a network, an MMEdownloads user's subscription information from an HSS and then generatesdefault bearer with a corresponding PDN using subscriber QoS profile.

SDF QoS: QCI (QoS Class Identifier) and ARP (Allocation and RetentionPriority) are basic parameters applied to all SDFs. QCI is an expressionwith integer values (1 to 9) by standardizing different QoS properties.And, the standardized QoS properties may be represented as resourcetype, priority, packet delay budget, packet error loss rate and thelike. The SDF may be categorized into a GBR type SDF having a networkresource allocated fixedly or a non-GBR type SDF having a networkresource not allocated fixedly in accordance with a resource type.Besides QCI and ARP, GBR (Guaranteed Bit Rate) and MBR (Maximum BitRate) are assigned as QoS parameters to the GBR type SDF and MBR isassigned to the non-GBR type SDF.

GBR type SDF QoS parameter: QCI, ARP, GBR (DL/UL), MBR (DL/UL)

Non-GBR type SDF QoS parameter: QCI, ARP, MBR(DL/UL)

SDF is mapped to EPS bearer by P-GW and is then delivered to UE throughthe EPS bearer. SDFs (SDF aggregate) having the same QCI and ARP aremapped to one EPX bearer.

EPS Bearer QoS: QCI and ARP are basic QoS parameters applied to all EPSbearers. EPS bearer is categorized into GBR type bearer or non-GBR typebearer in accordance with QCI resource type. A default bearer is alwaysnon-GBR type and a dedicated bearer may be set to GBR or non-GBR. GBRtype bearer QoS parameters may include QCI, ARP, GBR (DL/UL), and MBR(DL/UL). Non-GBR type bearer QoS parameters may include QCI, ARP,APN-AMBR (DL/UL), and UE-AMBR (DL/UL).

Besides QCI and ARP, the GBR type bearer has GBR and MBR as QoSparameters, which means that a fixed resource is allocated per bearer.On the other hand, the non-GBR type bearer has AMBR (Aggregated MaximumBit Rate) as QoS parameter, which means that a maximum bandwidth usabletogether with other non-GBR type bearers is assigned instead ofreceiving resource application per bearer. APN-AMBR is a maximumbandwidth that may be shared within the same PDN by non-GBR type bearersand UE-AMBR is a maximum bandwidth sharable within the same UE. In casethat UE has several PDN connections, a sum of APN-AMBRs of the PDNscannot exceed UE-AMBR.

In the following description, definition of a trigger condition for asecondary system (e.g., AP) measurement is explained. In particular, atrigger condition for a UE to initiate other RAT measurement isdescribed.

(1) A condition for a UE to start a measurement of neighbor AP in a stepof not starting a measurement may be determined by a traffic transmittedon radio resource configuration) (e.g., DRB (Data Radio Bearer)addition. The condition may be determined in accordance with GBR,non-GBR or a new EPS bearer QoS type defined by the present invention.If a traffic desired to be transmitted via AP in case of Multi-RATCapability Negotiation (S410, or S420 to S450) is defined and isgenerated through radio resource configuration, the UE may start the APmeasurement.

(2) If IEEE 802.11 (WLAN, AP) is selected as a preferred system in radioresource configuration, a UE may start a measurement of neighbor AP.

Meanwhile, a metric for starting a measurement may be transmitted as aUE-specific value to a UE by an eNB through a unicast message. In thefollowing description, a traffic type used to determine a triggercondition for a secondary system (e.g., AP) measurement is explained.

Traffic Characteristics in LTE

As traffics transmitted on a cellular network are diversified, if an eNBis aware of traffic characteristics and processes radio bearersappropriately, it may help enhancement of total system performance. Yet,a current LTE system discriminates a service data flow (SDF) on APN(p-GW) level only in accordance with a specific QoS policy, defines aQoS level, and then provides a service appropriate for it.

P-GW SDF-QoS-defines a service data flow sorted by 5-tuple (Source IP,Destination IP, Source Port number, Destination Port number, ProtocolID) in accordance with a QoS policy. The SDF QoS is mapped again to EPSbearer QoS. Currently, there are two types (default, dedicated) of EPSbearers in LTE.

Referring to FIG. 5, an eNB or LTE system defines LTE EPS bearer on asub-divided QoS level using the corresponding SDF QoS definition and theeNB may provide a different service for each of the types. To this end,like SDF QoS, EPS bearers may be sorted by the following types (EPSbearer QoS types).

Ex.) voice (Conversational Real Time service), streaming video(streaming real time service), web browsing (Interactive BE service),telemetry/emails (Background BE service)

EPS Bearer type 1: This type corresponds to a default EPS bearer that isbasically generated when a connection is established.

EPS Bearer type 2: Best Effort Service type

EPS Bearer type 3: Real time service

. . . .

EPS Bearer type n: Streaming video service

FIG. 6 is a diagram to describe a system selecting method using QoSclass defined in LTE.

Referring to FIG. 6, steps S605 to S630 sequentially correspond to theformer steps S410 to S460 shown in FIG. 4, respectively. And, thecontents of the S410 to S460 described with reference to FIG. 4 may beapplied to the steps S605 to S630.

Subsequently, a UE may receive an RRC connection reconfiguration message(e.g., RRCConnectionReconfiguration message) from an eNB [S635]. A dataradio bearer (DRB) may be transmitted in a manner of being added to theRRC connection reconfiguration message. As mentioned in the foregoingdescription of the trigger condition (1) for the UE to initiatemeasurement of a different radio access technology, whether to trigger ameasurement of neighbor AP may be determined by a traffic typetransmitted through the radio resource configuration (e.g., DRBaddition). And, the trigger condition may be determined in accordancewith GBR, Non-GBR, or a new EPS bearer QoS type (or traffic type)defined by a technology of the invention.

Thus, if a type of a traffic transmitted by being included in theRRCConnectionReconfiguration message corresponds to a traffic type thatmeets the trigger condition, the UE may perform a measurement on a basestation (e.g., neighbor APs (AP1, AP2, AP3) shown in FIG. 6) that uses adifferent radio access technology [S640]. Thereafter, the UE reports aresult of the measurement to the eNB [S645].

System Selecting Method Using QoS Class Defined in LTE

The technology of the present invention enables an eNB (or such anetwork entity as MultiRAT Management entity) to select a systemappropriate for a traffic using EPS bearer type defined in the foregoingdescription. It may be difficult to select an appropriate system usingthe previous classification reference (i.e., GBR, non-GBR) for dataflow. The technology of the present invention may determine an eNB totransmit a specific traffic type (or specific flow(s)) to a network(e.g., WLAN, i.e., a secondary system), which uses a radio accesstechnology different from that of an LTE network in accordance withinformation received from a UE using the EPS bearer type defined in theforegoing description. To this end, the eNB delivers the traffic, whichwas transmitted in the step S620 and corresponds to a traffic typedesired to be received via WLAN, to the AP. Subsequently, the UEreceives the traffic, which corresponds to the traffic type desired tobe received via the WLAN, from the AP and is also able to receive atraffic corresponding to another traffic type via LTE network at thesame time.

If a network entity or eNB below S-GW manages flows of a multi-RAT UE,an RAT selection for a traffic (or flow) of the UE is performed in afollowing manner. First of all, an eNB receives information on a network(e.g., a secondary system), which uses a different radio accesstechnology, from the UE. Secondly, the eNB analyzes the receivedinformation in a manner of comparing it to information on a serving cell(i.e., a cell in a currently connected primary system). Finally, the eNBselects an RAT for maximizing overall system performance. According tothe present invention, the eNB is assumed as becoming a subject for theselection.

If a network entity above P-GW is capable of managing RAT of a UE, thecorresponding network entity should be able to receive state informationof the UE and state information of a heterogeneous network such as acellular network, WLAN and the like. When traffic characteristicsdesired to be transmitted via wireless LAN (i.e., an access capable RATin accordance with capability of UE) are shared between a UE and an eNBin case of multi-RAT capability negotiation, if a specific traffic isgenerated and corresponds to a traffic preferred to be transmitted viathe wireless LAN (i.e., secondary system), the eNB controls a state ofthe wireless LAN (i.e., secondary system) to be searched using the aboveinformation.

Measurement Report

A data connection transmitted from an eNB to a UE is established by anRRC (radio resource configuration) procedure. Assuming that data for aspecific RB (radio bearer) or LC (logical channel) is transmitted via asecondary system (e.g., AP) under the determination made by the eNB, ifit is determined that the specific RB or LC needs to communicate withthe secondary system (e.g., AP), the eNB may instruct the UE to scanneighbor APs.

In doing so, the eNB sends an RRCConnectionReconfiguration message tothe UE, whereby the UE may initiate a measurement. In particular, the UEmay initiate the measurement of AP by an active scanning (e.g., ProbeRequest transmission and Probe Response reception) or a passive scanning(e.g., Beacon reception).

In the RRCConnectionReconfiguration message, at least one of MeasurementConfiguration and Radio Resource Configuration may be included. TheMeasurement Configuration may include information for a UE to find asecondary system quickly. For instance, the Measurement Configurationmay include at least one of SSID of AP neighbor to the UE, a beacontransmission cycle, and a measurement gap information. The RadioResource Configuration may carry a field for indicating trafficcharacteristics of a generated RB. For instance, in the Radio ResourceConfiguration, such a parameter value indicating traffic characteristicsas EPS bearer QoS type, QCI, ARP GBR (DL/UL), MBR (DL/UL) and the likemay be included.

If a trigger condition for a secondary system measure is alreadydefined, the UE may initiate the measurement of AP on the condition thatthe trigger condition is met irrespective of a presence or non-presenceof the reception of the RRCConnectionReconfiguration message from theeNB.

It may be unnecessary for the Measurement Configuration of theRRCConnectionReconfiguration message, which is mentioned in the abovedescription, to include the information on the measurement gap all thetime. In some cases, the information on the measurement gap may beomitted from the Measurement Configuration. This is described in detailwith reference to FIG. 7 as follows.

FIG. 7 is a diagram for one example to describe a measurement gap in LTEsystem. A UE may use InterFreqRSTDMeasurementIndication message toinstruct a network to start or stop a measurement of RSTD (ReferenceSignal Time Difference) between OTDOA (Observed Time Difference OfArrival) frequency bands requiring a measurement gap.

If it is indicated that an upper layer starts the inter-frequency bandRSTD measurement only, the UE is able to confirm a measurement gaprequired situation as soon as receive the indication from the upperlayer. If a sufficient gap is available at this timing point, the UE mayskip the transmission of the InterFreqRSTDMeasurementIndication message.Thereafter, even if the measurement gap gets insufficient, the UE mayskip the transmission of the InterFreqRSTDMeasurementIndication messageunless receiving a new indication from the upper layer.

If the upper layer indicates to stop performing the inter-frequency bandRSTD measurement, the UE may send the InterFreqRSTDMeasurementIndicationmess age despite having skipped the transmission of theInterFreqRSTDMeasurementIndication message in response to the previousindication indicating to start the inter-frequency band RSTDmeasurement.

Thus, it is necessary for a sufficient measurement gap to be configuredfor an inter-frequency band RSTD measurement in a switching basedmulti-RAT access system. Yet, the present invention relates to anon-switching based multi-RAT access system. According to the presentinvention, since a UE may access a secondary system without transferringa primary system, a measurement of the secondary system may be possiblewithout configuring a measurement gap. Therefore, information on themeasurement gap may be omitted from Measurement configuration ofRRCConnectionReconfiguration.

The UE may set a given DRB as a single measurement object as well as agiven frequency. In this case, the UE may explicitly indicate themeasurement object in accordance with a radio access technology type(e.g., E-UTRAN, UTRAN, CDMA2000, GERAN, WLAN, etc.). In this case, athird layer may filter a measurement result on a first layer. Asmentioned in the foregoing description, the inter-frequency bandmeasurement may be performed in an idle interval including themeasurement gap. Yet, a measurement of wInter-RAT (i.e., secondarysystem) may be performed without a measurement gap.

Generally, in order to maintain an optimal access to a base station, aUE should perform a measurement on at least one of a serving basestation and a neighbor base station to switch from a specific RAT toanother RAT. The UE measures the serving base station and the basestation in response to an indication of an eNB and is able to report aresult of the measurement to the eNB.

Yet, if the result of the measurement of the at least one of the servingbase station and the neighbor base station is insignificant, themeasurement result may not be transmitted to the eNB. For instance, if asignal of the neighbor base station is considerably lower than that ofthe serving base station, it is able to raise system efficiency by notreporting the measurement result. Hence, only if a trigger condition ofthe measurement result is met, the UE may transmit the measurementresult for the at least one of the serving base station and the neighborbase station to the eNB.

For instance, FIG. 8 is a flowchart of a process for a UE to report ameasurement result to an eNB. Referring to FIG. 8, a UE receives RRCConfiguration Reconfiguration message from an eNB [S801]. The UEperforms a measurement [S802]. And, the UE may report a measurementresult to the eNB using Measurement Report message [S804]. In doing so,the UE determines whether the following trigger condition is met [S803].Only if the trigger condition is met, the UE may report a result of themeasurement of at least one of a neighbor base station and a servingbase station to the eNB.

A1: Serving base station gets better than a first threshold (threshold1).

A2: Serving base station gets worse than the first threshold.

A3: Neighbor base station gets better then PCell (primary cell) byoffset.

A4: Neighbor base station gets better than a second threshold (threshold2).

A5: PCell gets worse than the first threshold and the neighbor basestation gets better than the second threshold.

A6 (not shown in the drawing): Neighbor base station gets better thanSCell (secondary cell) by offset (in CA (Carrier Aggregation)environment).

According to the present invention, a UE is not switched from a specificRAT to another RAT. Instead, while the UE maintains an access to aspecific RAT (e.g., primary system), the present invention enables anaccess to another RAT (e.g., secondary system). Hence, measurementobjects and reporting trigger conditions different from theabove-enumerated A1 to A5 are applicable.

FIG. 9 is a diagram for one example to describe a measurement object anda report configuration for a measurement result. Referring to FIG. 9, aUE may set a frequency or DRB given per radio access technology as ameasurement object. For instance, in a switching based multi-RAT accessenvironment, a specific frequency (or cell) is a measurement object likea single E-UTRA carrier frequency, a set of cells on a single UTRAcarrier frequency, a set of cells GERAN carrier frequencies, a set ofcells on a single (HRPD or 1xRTT) carrier frequency and the like. On theother hand, in a non-switching based multi-RAT access environment likethe present invention, a frequency may be set as a measurement objectlike a set of WLAN carrier frequencies or a DRB may be set as ameasurement object like a set of E-UTRA data barriers (or flows) on asingle E-UTRA carrier frequency, a set of WLAN data bearers (or flows)on a single WLAN carrier frequency and the like.

The UE gives a measurement ID for identifying a result of measurement ofresult of a measurement object and is then able to report themeasurement ID given measurement result to the eNB. The measurementresult reporting may occur periodically. Alternatively, the measurementresult reporting may occur if a trigger condition for the reporting ismet.

In the non-switching based multi-RAT access environment, a UE may reporta measurement result of a secondary system if the following triggercondition occurs.

B1: Case that an inter-RAT neighbor gest better than a second threshold.

B2: Case that PCell gets worse than a first threshold and an inter-RATneighbor gets better than the second threshold.

B3: Case that an inter-RAT serving gets worse than the first threshold.

In the above enumerated conditions B1 to B3, the inter-RAT may mean abase station (e.g., AP) of a secondary system. When a serving basestation of a UE is a base station (e.g., eNB) of a primary system, theinter-RAT serving neighbor may mean that a serving base station of theUE is a base station (e.g., AP) of a secondary system.

FIG. 10 is a diagram of enumerated trigger conditions. A1 to A10diagrammatize the trigger conditions in a switching based multi-RATaccess environment. And, B1 to B3 diagrammatize the trigger conditionsin a non-switching based multi-RAT access environment. In this case, afirst threshold may be provided to determine whether a measurementresult of a primary system (or a serving base station) is meaningful.And, a second threshold may be provided to determine whether ameasurement result of a secondary system (or a neighbor base station) ismeaningful.

A parameter value for a trigger condition for reporting may betransmitted to a UE via a reportConfigInterRAT message. In particular,the reportConfigInterRAT message may be broadcasted or unicasted to aUE. When a measurement object is a DRB, the reportConfigInterRAT may betransmitted as UE-specific information to the UE by unicast.

The trigger conditions may be set to different values for eachmeasurement object. For instance, each of the first and secondthresholds may be defined as a different value depending on preferenceof AP or traffic characteristics of DRB.

For instance, a voice traffic may prefer to communicate via a primarysystem (e.g., a cellular network) rather than a secondary system (e.g.,WLAN network). And, a data traffic may prefer to communicate via asecondary system rather than a primary system. Hence, a threshold value(e.g., a second threshold) for reporting a measurement result of thesecondary system may be set high for the voice traffic. And, a thresholdvalue (e.g., a second threshold) for reporting a measurement result ofthe secondary system may be set low for the data traffic. Thus, as thethreshold values for reporting the measurement result may vary dependingon a transmitted traffic, trigger conditions may be defined andtransmitted in accordance with the traffic characteristics. As mentionedin the above description, the trigger condition may be defineddifferently in accordance with a traffic type (e.g., EPS bearer QoStype) of flow or traffic characteristics (e.g., GBR, non-GBR, etc.) offlow.

An eNB may provide a UE with a trigger condition for a reporting throughRRCConnectionReconfiguration message. In particular, the eNB may providethe UE with the trigger condition through measConfig./radioResourceConfgof RRCConnectionReconfiguration. In case that the trigger conditions isdefined in accordance with a traffic type or traffic characteristics offlow, the trigger condition for each flow (or RB) may be transmitted tothe UE. In doing so, the eNB may transmit an appropriate triggercondition to the UE by unicast with reference to characteristics of atraffic transmitted through radio resource configuration.

Based on the trigger condition for the reporting, whether to report ameasurement result may be determined or set in case of multi-RATcapability negotiation between the UE and the eNB.

For instance, although a signal strength of AP is lower than a threshold(e.g., second threshold) determined by the trigger condition, if a userintends to communicate using the AP, it may be necessary to report ameasurement result of the AP irrespective of whether the triggercondition is met.

Hence, the UE may indicate whether the measurement result will bereported by the trigger condition in case of the multi-RAT capabilitynegotiation. In particular, the UE may use ‘measurement reporting bytrigger condition’ bit of UECapabilityInformation message to indicatewhether the measurement result of the AP will be reported by the triggercondition. For instance, when a value of the ‘measurement reporting bytrigger condition’ bit is set to 1, the measurement result of the AP isreported only if the trigger condition for the reporting is met. When avalue of the ‘measurement reporting by trigger condition’ bit is set to1, despite that the trigger condition for the reporting is not met, ifthe AP is detected, the UE may report the measurement result of the AP.In doing so, the UE may report a measurement result of a preferred APamong the detected APs only to the eNB.

The UE may report the measurement result of the detected AP to the eNB.In this case, the measurement result of the AP may include at least oneof a channel state information (e.g., RSSI (Received Signal StrengthIndicator), RCPI (Received Channel Power Indicator), RSNI (ReceivedSignal to Noise Indicator), etc.) and a preferred AP information.

For instance, Table 2 shows one example of a measurement result reportmessage (Measurement Report message) sent to an eNB by a UE.

TABLE 2 1> set the measId to the measurement identity that triggered themeasurement reporting; 1> set the measResultPCell to include thequantities of the PCell; 1> set the measResultServFreqList to includefor each SCell that is configured, if any, within measResultSCell thequantities of the concerned SCell; 1> if the reportConfig associatedwith the measId that triggered the measurement reporting includesreportAddNeighMeas:    2> for each serving frequency for whichmeasObjectId is referenced in the measIdList, other than the frequencycorresponding with the measId that triggered the measurement reporting:    3> set the measResultServFreqList to include withinmeasResultBestNeighCell the physCellId and the quantities of the bestnon-serving cell, based on RSRP, on the concerned serving frequency;1> if there is at least one applicable neighbouring cell to report:   2> set the measResultNeighCells to include the best neighbouringcells up to maxReportCells in accordance with the following:     3> ifthe triggerType is set to event:      4> include the cells included inthe cellsTriggeredList as defined within the VarMeasReportList for thismeasId;     3> else:      4> include the applicable cells for which thenew measurement results became available since the last periodicalreporting or since the measurement was initiated or reset; 3> for eachcell that is included in the measResultNeighCells, include thephysCellId; 3> if the triggerType is set to event; or the purpose is setto reportStrongestCells or to reportStrongestCellsForSON:   4> for eachincluded cell, include the layer 3 filtered measured results inaccordance with the reportConfig for this measId, ordered as follows:   5> if the measObject associated with this measId concerns E-UTRA:    6> set the measResult to include the quantity(ies) indicated in thereportQuantity within the concerned reportConfig in order of decreasingtriggerQuantity, i.e. the best cell is included first;    5> if themeasObject associated with this measId concerns UTRA FDD and ifReportConfigInterRAT includes the reportQuantityUTRA-FDD:     6> set themeasResult to include the quantities indicated by thereportQuantityUTRA-FDD in order of decreasing measQuantityUTRA-FDDwithin the quantityConfig, i.e. the best cell is included first;    5>if the measObject associated with this measId concerns UTRA FDD and ifReportConfigInterRAT does not include the reportQuantityUTRA-FDD; or   5> if the measObject associated with this measId concerns UTRA TDD,GERAN or CDMA2000:     6>set the measResult to the quantity asconfigured for the concerned RAT within the quantityConfig in order ofeither decreasing quantity for UTRA and GERAN or increasing quantity forCDMA2000 pilotStrength, i.e. the best cell is included first;    5> ifthe measObject associated with this measId concerns WLAN and ifReportConfigInterRAT includes the reportQuantityWLAN:     6>set themeasResult to include the quantities indicated by the reportQuantityWLANin order of decreasing measQuantityWLAN within the quantityConfig, i.e.the best cell is included first. 3> else if the purpose is set toreportCGI:   4> if the mandatory present fields of the cgi-Info for thecell indicated by the cellForWhichToReportCGI in the associatedmeasObject have been obtained:    5> if the cell broadcasts a CSGidentity:     6>include the csg-Identity;     6>include thecsg-MemberStatus and set it to member if the cell is a CSG member cell;   5> if the si-RequestForHO is configured within the reportConfigassociated with this measId:     6>include the cgi-Info containing allthe fields that have been successfully acquired, except for theplmn-IdentityList;    5> else:     6>include the cgi-Info containing allthe fields that have been successfully acquired; 1>if theue-RxTxTimeDiffPeriodical is configured within the correspondingreportConfig for this measId;    2> set the ue-RxTxTimeDiffResult to themeasurement result provided by lower layers;    2> set the currentSFN;1> if the includeLocationInfo is configured in the correspondingreportConfig for this measId and detailed location information that hasnot been reported is available, set the content of the locationInfo asfollows:    2> include the locationCoordinates;   2>if available,include the gnss-TOD-msec; 1> increment the numberOfReportsSent asdefined within the VarMeasReportList for this measId by 1; 1> stop theperiodical reporting timer, if running; 1> if the numberOfReportsSent asdefined within the VarMeasReportList for this measId is less than thereportAmount as defined within the corresponding reportConfig for thismeasId:   2>start the periodical reporting timer with the value ofreportInterval as defined within the corresponding reportConfig for thismeasId; 1> else:   2>if the triggerType is set to periodical:    3>remove the entry within the VarMeasReportList for this measId;    3>remove this measId from the measIdList within VarMeasConfig; 1> if themeasured results are for CDMA2000 HRPD:  2> set thepreRegistrationStatusHRPD to the UE's CDMA2000 upper layer's HRPDpreRegistrationStatus; 1> if the measured results are for CDMA20001xRTT:  2> set the preRegistrationStatusHRPD to FALSE; 1> submit theMeasurementReport message to lower layers for transmission, upon whichthe procedure ends;

Referring to Table 2, if a measurement object for a random measurementID is related to WLAN and a reportConfigInterRAT message contains a WLANreport quantity (reportQuantityWLAN), a UE may set measResult includinga quantity indicated by the reportQuantityWLAN in decreasing order ofmeasQuantityWLAN within quantityConfig. In doing so, the UE may controla best cell to be situated at a first place in the measResult. Aparameter value for a trigger condition for reporting may be transmittedto the UE via reportConfigInterRAT message.

When a UE detects at least two APs, if an eNB receives a measurementresult of the at least two APs, the eNB selects an AP appropriate forthe UE from a plurality of APs and is then able to inform the UE of theselected AP. When the eNB selects the AP appropriate for the UE, atleast one of the following metrics may be used.

i) Same Operator: Preferentially select AP of the same operator of UE

ii) UE's Priority: Preferentially select AP preferred by UE

iii) Channel quality: Preferentially select AP having a good channelstate

iv) Load balancing: Select AP by considering load distribution

v) Carried traffic: Select AP by considering traffic

The eNB may send indication, which indicates an AP to be accessed, tothe UE using the above enumerated metrics.

Secondary System Management

As mentioned in the foregoing description with reference to FIG. 4 andFIG. 6, after the scanning of the secondary system, the secondary systemmanagement procedure is initiated for example. The secondary systemmanagement procedure may be mainly divided into a secondary systemadding procedure, a secondary system deleting procedure and a secondarysystem changing procedure. Prior to the description of each of theprocedures, messages used for the secondary system shall be described asfollows.

FIG. 11 is a flowchart to describe a message defined for a secondarysystem management procedure. Having detected a secondary system thatmeets a preset condition, a UE may send a message for requesting anassociation with an AP to an eNB [S1110]. This message may be named aSecondarySystemRequest message.

Having received the SecondarySystemRequest message from the UE, the eNBchecks states of APs and is then able to select an AP that the UE willaccess [S1120]. Subsequently, in response to a request made by the UE,the eNB may send a message for indicating an access to a secondarysystem to the UE [S1130]. This message may be called aSecondarySystemSetup message. Information (e.g., identificationinformation of the selected AP, authentication method with the selectedAP, etc.) on an AP that the UE to be accessed, DRB (or flow) informationto be transmitted to the secondary system, and the like may be includedin the SecondarySystemSetup message. The UE transceives an associationrequest frame, an association response frame and the like with the APindicated by the SecondarySystemSetup message and is then able toattempt an access to the AP [S140]. In case that the secondary systemcorresponds to IEEE 802.11e, a traffic stream setup process(particularly, ADDTS request frame/ADDTS response frame transceiving)with the AP may be performed.

Thereafter, the UE may send a message for reporting a result ofconnection to the AP to the eNB [S1150]. This message may be named aSecondarySystemSetupComplete message. Through theSecondarySystemSetupComplete message, the UE may report a result ofmapping between a DRB ID (or flow ID) of a DRB, which is to betransmitted to the secondary system, and AID/TSID (associationID/traffic stream ID).

If the AP is successfully accessed, the UE may transceive data for aspecific traffic type via the AP. To this end, the eNB redirects a pathof DL data for the specific flow to the AP and the UE is able totransmit UL data for the DRB ID (or flow ID) indicated by the eNB not tothe eNB but to the AP. Data except the specific data type may betransceived via the eNB as it is.

Reassociation with the AP or Disassociation from the AP may be performedthrough the SecondarySystemSetup message and the SecondarySystemCompletemessage between the UE and the eNB. The reassociation with the AP meansthat the UE makes a handover into a neighbor AP. And, the disassociationfrom the AP means that the UE ends the access to the AP. In order tosecure seamless data transmission of the UE, the eNB may supportseamless flow mobility between the AP and the eNB or between APs.

For instance, although a UE has leaved a coverage of an AP, if there isno neighbor AP into which the UE will make a handover, in order tosecure that the data transmitted via a secondary system may betransmitted seamlessly, an eNB may support seamless flow mobilitybetween the AP and the eNB.

On the contrary, if the UE detects the neighbor AP to make a handoverinto, the UE may support seamless flow mobility between APs in order tosecure that data for a specific flow may be transmitted seamlessly.

A primary system performs such a basic control operation as an accesscontrol between UE and AP, a configuration of DRB and the like. And asecondary system transceives data (i.e., data for a specific traffictype) indicated by the primary system. In particular, all datatransmitted to a user equipment are configured by a radio resourceconfiguration procedure of RRCConnectionReconfiguration transmitted toUE by eNB. And, data for a specific RB may be transmitted to the UE viaAP under the determination made by the eNB. To this end, the eNB mayredirect the data, which are transmitted to specific RNTI (radio networktemporary identities) and specific DRB ID, among the data transmitted tothe eNB to the AP.

Based on the above description, a secondary system adding procedure, asecondary system deleting procedure and a secondary system changingprocedure are described in detail as follows.

Addition of Secondary System

FIG. 12 is a flowchart to describe an additional procedure of asecondary system. A secondary system adding procedure may be initiatedby a UE or a base station. FIG. 12 shows one example that a secondarysystem adding procedure is initiated by a UE. Having detected asecondary system that meets a preset condition, a UE may request anassociation (connection setup) with the detected secondary system viaSecondarySystemRequest message [S1210]. In doing so, one of thefollowing conditions may be set as the preset condition. First of all, aUE-preferred AP is detected. Secondly, a measured signal strength of aAP is sufficiently high (e.g., a preferred AP is detected and ameasurement result of the preferred AP is higher than a presetthreshold, or a measurement result of AP is higher than a measurementresult of eNB, etc). Thirdly, a specific flow (or DRB) has established.

Having received the SecondarySystemRequest message from the UE, the eNBmay send a SecondarySystemSetup message indicating an access to thesecondary system in response to the request made by the UE [S1220].

By skipping the SecondarySystemRequest message sending step S1210 andsending a SecondarySystemSetup message to the UE, the secondary systemadding procedure may be initiated (i.e., a method for a base station toinitiate a secondary system adding procedure). In particular, ifrecognizing the establishment (i.e., DRB addition to UE) of a specificflow connection to the UE and the position of the UE located within anarea of the secondary system, the eNB sends a SecondarySystemSetupmessage irrespective of a presence or non-presence of a reception of theSecondarySystemRequest message, thereby instructing the UE to access thesecondary system [S1220].

In the SecondarySystemSetup message, at least one of information on theAP selected by the eNB, information on a flow (or DRB) to be transmittedto the secondary system, authentication information of the secondarysystem, information indicating whether to enter a doze mode afterassociation, timer information, action time information and a data unitinformation to be redirected to an AP (e.g., U-plane, APN unit, DRBunit, flow unit, data unit in specific flow, etc) may be included.

The selected AP information may indicate an identification informationof an AP that the UE will access. The flow (or DRB) information mayindicate a traffic type of a flow that the UE will transceive via theAP. The UE attempts an access to the AP indicated by the selected APinformation. If the access to the AP is successfully completed, the UEmay transceive the traffic type indicated by the flow information viathe selected AP.

The authentication information of the secondary system indicates apresence or non-presence of a shared key of the secondary system and theshared key. In case that the secondary system is an open system thatdoes not use the shared key, the UE may access the secondary systemwithout the shared key. On the other hand, if the secondary system is anencrypted system that uses the shared key, the UE may access thesecondary system using the shared key indicated by the authenticationinformation.

The information indicating whether to enter the doze mode indicateswhether the UE should enter a power saving mode after the associationwith the secondary system. If the UE has no data to receive from thesecondary system right now despite being associated with the secondarysystem, the eNB may instruct the UE to enter the doze mode after theassociation with the AP.

The timer information may indicate an expiry period until a timer forsecondary system association starting after the transmission of theSecondarySystemSetup message expires.

The action time information may indicate a timing point for the UE toinitiate the transceiving of data for a specific traffic type with theAP.

The data unit information may indicate a data unit (e.g., U-plane, APN,DRB, flow, flow in same flow) to be redirected to the AP. The data unitinformation may be an 1 bit indicator indicates whether the eNBretransmit all the flows to the AP. Or, the data unit information mayindicate a data unit (i.e., U-plane, unit of APN, unit of DRB, unit ofIP flow, unit of data in specific flow, etc) redirected to the AP. Ifthe data unit information indicates that the data unit redirected to theAP is set as a unit of data in specific flow, ratio informationindicates a ratio between amount of data in specific flow transmittedvia the eNB and amount of data transmitted via the AP may further beincluded in the SecondarySystemSetup message.

In response to the reception of the SecondarySystemSetup message, the UEmay send a SecondarySystemSetup ACK message [S1230]. Alternatively, theUE may attempt an access to the AP without sending the ACK message.

Having received the SecondarySystemSetup from the eNB, the UE mayattempt the access to the AP [S1240]. In particular, the UE may attemptthe access to the AP through the steps of synchronization,authentication and association with the AP.

The synchronization step is provided to match synchronization betweenthe UE and the AP. By receiving a beacon frame from the AP, the UE maymatch the synchronization with the AP.

The authentication step includes the steps of transmitting anauthentication request frame to the AP from the UE and transmitting anauthentication response frame to the UE from the AP in response. In casethat the AP is an open system, the authentication may be performedwithout utilizing a separate shared key. Otherwise, the authenticationmay be performed using a shared key.

After the UE has been successfully authenticated, the association stepmay be performed. In particular, the association step includes the stepsof transmitting an association request frame to the AP from the UE andtransmitting an association response message to the UE from the AP inresponse. In this case, AID (association ID) information on the UE maybe included in the association response frame.

In case that the secondary system includes IEEE 802.11e system, the UEmay perform a traffic stream (TS) setup. For the traffic stream setup,the UE receives an ADDTS request from the AP and is then able totransmit an ADDTS response to a specific AP in response to the request.

In order to report a result of the connection to the AP, the UE may senda SecondarySystemSetupComplete message [S1250]. The UE configures aSecondarySystemSetupComplete message to contain a status valueindicating a success or failure in the access to the AP. Subsequently,the UE is always able to send the SecondarySystemSetupComplete messageirrespective of the success or failure in the result of the connectionto the AP. Alternatively, the UE may send theSecondarySystemSetupComplete message only if the access to the AP issuccessful.

For instance, if the SecondarySystemSetupComplete message contains thestatus value, the UE adjusts the status value to indicate whether theestablishment of the connection to the AP is successful.

For another instance, only if the establishment of the connection to theAP is successful, the UE may send the SecondarySystemSetupCompletemessage. After the SecondarySystemSetupComplete message has been sent,if the SecondarySystemSetupComplete message is received within aprescribed time, the eNB may determine that the UE has successfullyaccessed the AP. On the contrary, after the SecondarySystemSetupCompletemessage has been sent, if the SecondarySystemSetupComplete message isnot received within the prescribed time, the eNB may determine that theUE has not accessed the AP successfully.

After sending a SecondarySystemSetup message, the eNB may start asecondary system association timer. If not receiving theSecondarySystemSetupComplete message until the expiration of thesecondary system association timer, the eNB may determine that the UEfails in the access to the AP. Using the timer information of theSecondarySystemSetup message, the UE may recognize an expiry timingpoint of the secondary system association timer. In order to secure atime enough for the UE to send the SecondarySystemSetupComplete message,the expiry period of the secondary system association timer may bedetermined in consideration of a time taken for the association betweenthe UE and the AP.

The SecondarySystemSetupComplete message may contain information on anaddress (e.g., IP address assigned to the UE by the AP) assigned to theUE by the AP.

If the establishment of the connection to the AP is not successful, theeNB newly selects an AP and may be then able to resend aSecondarySystemSetup message to the newly selected AP in order toindicate an access to the newly selected AP. Having received the re-sentSecondarySystemSetup message, the UE may attempt the access to the newlyselected AP indicated by the re-received SecondarySystemSetup message.

If the establishment of the connection to the AP is successful, the UEmay transceive data for a specific traffic type via the AP and is ableto transceive data for other traffic types via the eNB [S1260]. Thetraffic type to be transceived via the AP may be indicated by DRBinformation (or flow information) of the SecondarySystemSetup message.In order for downlink data of the specific traffic type to betransmitted via the AP, the eNB may redirect the downlink data for thespecific traffic type to the AP. To this end, the eNB may set adestination of the data for the specific data type to an address (e.g.,IP address assigned to the UE by the AP) of the UE. The UE may transmituplink data for the specific traffic type to the AP. eNB (orinterworking entity) may redirect a downlink data to UE by transmittinga specific message to an entity which manages IP information on a flowof UE (e.g., P-GW or terminal end). The specific message may be a flowIP address binding update message which comprises an action timeinformation. Action time information included in the flow IP addressbinding update message may be same as an action time message included inSecondarySystemSetup messages transmitted from the eNB to UE. In thiscase, the eNB (or an interworking entity) may redirect a downlink datato an AP by transmitting a specific message to a main entity (e.g., P-GWor a UE situating at an end) managing IP information on a flow of theUE. In this case, the transmitted specific message may correspond to aFlow-IP address binding update message and action time information maybe included in the message. The action time information included in theFlow-IP address binding update message and action time information of aSecondarySystemSetup message, which is transmitted to the UE by the eNB,may indicate identical timing.

In doing so, the eNB may designate an action time that is a timing pointat which the UE starts the transceiving of the data for the specifictraffic type via the AP. Even if the establishment of the connection tothe AP is successful, the UE may not perform the transceiving of thedata for the specific traffic type via the AP until an action timecomes. If the SecondarySystemSetup message is lost, the eNB is unable torecognize whether the UE has been successfully accessed the AP.Nonetheless, if the UE intends to transceive the data for the specifictraffic type via the AP, since the eNB is unable to change or redirectthe path of the data for the specific traffic type to the AP, the UE mayhave a problem in receiving the downlink data for the specific traffictype appropriately.

Hence, the eNB designates the action time. The eNB is then able tocontrol the UE to start the transceiving for the specific traffic typewith the AP only if the action time expires. In this case, the actiontime may be calculated in consideration of the expiry period of thesecondary system association timer and a time taken for theretransmission of the SecondarySystemSetup message due to the failure inaccessing the AP. In particular, after the SecondarySystemSetup messagehas been sent, the action time may be set to a time after elapse of atime equal to or greater than a sum of the expiry period of thesecondary system association timer and the time taken for thetransmission of the SecondarySystemSetup message.

Change of Secondary System

FIG. 13 is a flowchart to describe a changing procedure of a secondarysystem. If a UE leaves a coverage of an accessed AP or an AP having ameasurement higher than that of the accessed AP is detected, an eNB mayinstruct the UE to make a handover into a new AP. For clarity of thefollowing description, an AP currently providing a service to the UEshall be named a serving AP or an old AP and a new AP becoming ahandover target shall be named a target AP or a new AP. In order toinstruct the UE to make a handover into a new AP, the eNB may send aSecondarySystemSetup message to the UE [S1310]. The SecondarySystemSetupmessage sent to the UE may include at least one of an information on atarget AP, an information on a flow (or DRB) to be transmitted via asecondary system, an authentication information of the secondary system,an information indicating whether to enter a doze mode afterassociation, a timer information, a disconnection time information, anaction time information and a data unit information to be redirected toan AP (U-plane, APN, DRB, flow, data in same flow).

The target AP information may indicate an identification information ofa new AP that the UE will newly access. And, the flow (or DRB)information may indicate a traffic type of a flow to be transceived bythe UE via the new AP. The authentication information of the secondarysystem may indicate a presence or non-presence of a shared key of thenew AP and the shared key. The information indicating whether to enterthe doze mode may indicate whether the UE should enter a power savingmode after the association with the new AP. The timer information mayindicate an expiry period until expiration of a secondary systemreassociation timer after sending the SecondarySystemSetup message. Thedisconnection time information may indicate a timing point at which theUE is disassociated from the old AP. Or, the disconnection timeinformation may indicate a timing point at which the eNB stopsredirecting data for specific flow to the old AP. The action timeinformation may indicate a timing point at which the UE may start thetransceiving of data for a specific traffic with the new AP. Or, theAction information may indicate a timing point at which the eNBredirects data for specific flow which stopped redirecting at the timingpoint indicated by the disconnection time information to the new AP. Thedata unit information may indicate a data unit (e.g., U-plane, APN, DRB,flow, flow in same flow) to be redirected to the AP.

eNB may transmit a Flow-IP address binding update message whichcomprises a disconnection time information and an action timeinformation to an entity which manages IP information on a flow of UE(e.g., P-GW or terminal end) in course of (or after) transmitting theSecondarySystemSetup message. The entity which received the Flow-IPaddress binding update message (e.g., P-GW) may newly set an IP addressof data on a specific flow to be transmitted to UE based on thedisconnection time information and the action time information.

While the reassociation procedure of the UE is in progress through acontrol connection (e.g., a backhaul control connection, a radio controlconnection, etc.) between the old AP and the new AP, the eNB maytransmit a security information set by the old AP to the new AP.

In response to the reception of the SecondarySystemSetup message, the UEsends a SecondarySystemSetup ACK message [S1320] or may disconnect theaccess from the old AP without sending the ACK message.

Having received the SecondarySystemSetup message, the UE may disconnectthe connection from the old AP [S1330]. In doing so, the UE maydisconnect the connection from the old AP at the disconnection timingpoint indicated by the disconnection time information. Once thedisconnection timing point is designated through the disconnection timeinformation, the eNB may accurately obtain the timing point of thedisconnection between the UE and the old AP. Hence, the eNB mayaccurately calculate the timing point of terminating the redirection ofthe data for the specific traffic type to the old AP.

At the disassociation timing point, the UE may send a disassociationnotification message to the old AP. If an ACK message for thedisassociation notification message is received from the old AP, theconnection between the UE and the old AP may be terminated.

Once the connection to the old AP is terminated, the UE may attempt anaccess to a new AP [S1340]. In particular, the UE may be able to attemptthe access to the new AP through synchronization, authentication andassociation with the new AP.

In order to report a result of the connection to the new AP, the UE maysend a SecondarySystemSetupComplete message [S1350]. The UE configures aSecondarySystemSetupComplete message to contain a status valueindicating a success or failure in the access to the new AP.Subsequently, the UE is always able to send theSecondarySystemSetupComplete message irrespective of the success orfailure in the result of the connection to the new AP. Alternatively,the UE may send the SecondarySystemSetupComplete message only if theaccess to the new AP is successful.

For instance, if the SecondarySystemSetupComplete message contains thestatus value, the UE adjusts the status value to indicate whether theestablishment of the connection to the new AP is successful.

For another instance, only if the establishment of the connection to thenew AP is successful, the UE may send the SecondarySystemSetupCompletemessage.

The eNB waits for the SecondarySystemSetupComplete message to be sentfrom the UE for a while. If the eNB receives theSecondarySystemSetupComplete message, the eNB determines that the UE hassucceeded in the access to the AP. On the contrary, after theSecondarySystemSetupComplete message has been sent, if theSecondarySystemSetupComplete message is not received within a prescribedtime, the eNB may determine that the UE has failed in the access to theAP. After sending a SecondarySystemSetup message, the eNB may start asecondary system reassociation timer. If not receiving theSecondarySystemSetupComplete message until the expiration of thesecondary system reassociation timer, the eNB may determine that the UEfails in the access to the new AP. In order to secure a time enough forthe UE to send the SecondarySystemSetupComplete message, the expiryperiod of the secondary system reassociation timer may be determined inconsideration of a time taken for the reassociation with the AP.

The SecondarySystemSetupComplete message may contain information on anaddress (e.g., IP address assigned to the UE by the AP) assigned to theUE by the new AP.

If the establishment of the connection to the new AP is not successful,the eNB newly selects a target AP and may be then able to resend aSecondarySystemSetup message to indicate an access to the newly selectedtarget AP. Having received the re-sent SecondarySystemSetup message, theUE may attempt the access to the newly selected target AP indicated bythe re-received SecondarySystemSetup message.

If the establishment of the connection to the AP is successful, the UEmay transceive data for a specific traffic type not via the old AP butvia the new AP [S1360]. The traffic type to be transceived via the newAP may be indicated by DRB information (or flow information) of theSecondarySystemSetup message. And, data other than the specific traffictype may be transceived via the eNB as they are.

As mentioned in the foregoing description with reference to FIG. 11, theeNB may designate an action time for the UE to initiate the transceivingof the data for the specific data type via the new AP [not shown in thedrawing]. Once the action time is designated, the UE may initiate thetransceiving for the specific traffic type with the new AP only if theaction time is up.

Deletion of Secondary System

FIGS. 14A to 14C are flowcharts to describe a deleting procedure of asecondary system. FIG. 14A and FIG. 14B are diagrams for examples that aUE is disassociated from an AP by an indication of an eNB. FIG. 14C is adiagram for one example that a UE is actively disassociated from an AP.

Referring to FIG. 14A and FIG. 14B, an eNB may send a UE aSecondarySystemSetup message to indicate disassociation from an AP[S1410 a, S1410 b]. The SecondarySystemSetup message may include atleast one of an information on a disassociated AP, an information on aflow (or DRB) transmitted from the disassociated AP, a disconnectiontime information, an action time information and a timer information.

The disassociated AP information may indicate an identificationinformation of an AP from which the UE will be disconnected. And, theflow (or DRB) information may indicate a traffic type of a flow handledby the AP to be disconnected.

The timer information may indicate an expiry period until expiration ofa secondary system disassociation timer that starts after sending theSecondarySystemSetup message.

The disconnection time information may indicate a timing point at whichthe UE is disassociated from the AP. And, the action time informationmay indicate a timing point at which the UE may start the transceivingof data for a specific traffic with the eNB.

In response to the reception of the SecondarySystemSetup message, the UEsends a SecondarySystemSetup ACK message [S1420 a, 1420 b] or maydisconnect the access from the AP without sending the ACK message.

Having received the SecondarySystemSetup message, the UE may terminatethe access from the AP [S1430 a, 1430 b]. In doing so, the UE maydisconnect the connection from the AP at the disconnection timeindicated by the disconnection time information. Once the disconnectiontime is designated through the disconnection time information, the eNBmay accurately obtain the timing point of the disconnection between theUE and the AP. Hence, the eNB may accurately calculate the timing pointof terminating the redirection of the data for the specific traffic typeto the AP.

At the disassociation timing point, the UE may send a disassociationnotification message to the AP. If an ACK message for the disassociationnotification message is received from the AP, the connection between theUE and the AP may be terminated.

Once the connection to the AP is terminated, in order to report that theconnection to the AP has been successfully terminated, the UE may send aSecondarySystemSetupComplete message [S1440 a]. The UE configures aSecondarySystemSetupComplete message to contain a status valueindicating a success or failure in the termination of the connection tothe AP. Subsequently, the UE is always able to send theSecondarySystemSetupComplete message irrespective of the success orfailure in the result of the termination of the connection to the AP.Alternatively, the UE may send the SecondarySystemSetupComplete messageonly if the termination of the connection to the AP is successfullycompleted.

For instance, if the SecondarySystemSetupComplete message contains thestatus value, the UE adjusts the status value to indicate whether theconnection to the AP is successfully terminated.

For another instance, only if the connection to the AP is successfullyterminated, the UE may send the SecondarySystemSetupComplete message.

The eNB waits for the SecondarySystemSetupComplete message to be sentfrom the UE for a while. If the eNB receives theSecondarySystemSetupComplete message, the eNB determines that the UE hassucceeded in the termination of the connection to the AP. On thecontrary, after the SecondarySystemSetupComplete message has been sent,if the SecondarySystemSetupComplete message is not received within aprescribed time, the eNB may determine that the UE has failed in thetermination of the connection to the AP. After sending theSecondarySystemSetup message, the eNB may start a secondary systemdisassociation timer. If not receiving the SecondarySystemSetupCompletemessage until the expiration of the secondary system disassociationtimer, the eNB may determine that the UE fails in the termination of theconnection between the UE and the AP. In order to secure a time enoughfor the UE to send the SecondarySystemSetupComplete message, the expiryperiod of the secondary system disassociation timer may be determined inconsideration of a time taken for the disassociation from the AP. Ifdetermining that the connection between the UE and the AP is notsuccessfully terminated, the eNB may resend the UE theSecondarySystemSetup message indicating the termination of theconnection to the AP.

Having sent the SecondarySystemSetupComplete message, the UE maytransceive data for a specific traffic type, which was transceived viathe AP, via the eNB [S1450 a]. In doing so, the UE may initiate thetransceiving of the data for a traffic type of a specific flow at theaction time indicated by the eNB.

For another instance, if the connection to the AP is terminated, the UEmay initiate the transceiving of the data for the traffic type of thespecific flow via the eNB immediately [S1440 b]. The step of sending theSecondarySystemSetupComplete message for reporting a result of thetermination of the connection to the AP may be skipped or theSecondarySystemSetupComplete message may be sent after initiation of thetransceiving of the data for the traffic type of the specific flow withthe eNB [S1450 b].

Referring to FIG. 14C, irrespective of the reception of theSecondarySystemSetup message from the eNB, the UE may terminate theconnection to the AP by itself [S1410 c]. Once the connection to the APis terminated, the UE may send a SecondarySystemSetupComplete message toindicate that the connection to the AP has been successfully terminated[S1420 c]. In particular, despite that a request for sending theSecondarySystemSetupComplete message is not made, the UE may send theSecondarySystemSetupComplete message to the eNB [unsolicited].

Having received the SecondarySystemSetupComplete message from the UE,the eNB stops redirection to the AP and may transmit the data for thetraffic type of the specific flow to the UE in direct.

According to various embodiments of the present invention, a UEsupporting both cellular and WLAN may efficiently select a heterogeneousnetwork for a flow via a control of a cellular network in a widebandwireless communication system.

The above-described embodiments may correspond to combinations ofelements and features of the present invention in prescribed forms. And,it may be able to consider that the respective elements or features maybe selective unless they are explicitly mentioned. Each of the elementsor features may be implemented in a form failing to be combined withother elements or features. Moreover, it may be able to implement anembodiment of the present invention by combining elements and/orfeatures together in part. A sequence of operations explained for eachembodiment of the present invention may be modified. Some configurationsor features of one embodiment may be included in another embodiment ormay be substituted for corresponding configurations or features ofanother embodiment. And, it is apparently understandable that a newembodiment may be configured by combining claims failing to haverelation of explicit citation in the appended claims together or may beincluded as new claims by amendment after filing an application.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention that come within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A method of supporting signal transmission andreception using two or more radio access technologies (RATs), which issupported by a user equipment, comprising: receiving a setup messageindicating access to a second base station in a second communicationnetwork supporting a second RAT from a first base station in a firstcommunication network supporting a first RAT; and attempting to accessthe second base station, wherein if the access to the second basestation is successfully performed, data on a specific traffic type istransmitted and received via the second base station, and data otherthan the specific traffic type is transmitted and received via the firstbase station.
 2. The method of claim 1, wherein the setup messagecomprises flow information indicating the specific traffic type, whichis to be transmitted and received via the second base station.
 3. Themethod of claim 3, wherein the setup message comprises action timeinformation indicating a time of communicating with the second basestation and wherein the user equipment begins to transceive data withthe second base station on a time indicated by the action timeinformation.
 4. The method of claim 1, further comprising transmitting acompletion message for reporting whether the access to the second basestation is successful, to the first base station.
 5. The method of claim4, wherein the completion message is transmitted only when the userequipment successfully accesses the second base station.
 6. The methodof claim 4, wherein the completion message comprises a status valueindicating whether the access to the second base station is successful.7. The method of claim 4, wherein the completion message comprises anaddress value assigned to the user equipment by the second base station.8. The method of claim 4, if the access to the second base stationfails, further comprising re-receiving the setup message indicating anaccess to a new second base station from the first base station.
 9. Themethod of claim 1, if the second base station of a predeterminedcondition is searched, further comprising transmitting a request messagerequesting an access to the second base station to the first basestation.
 10. The method of claim 1, wherein if the user equipmentdetects a second base station preferred by the user equipment, thepredetermined condition detects the preferred second base station andwherein the predetermined condition is configured by at least one of acase that a measurement result for the preferred second base station ishigher than a threshold and a case that a measurement result for thesecond base station is higher than a measurement result for the firstbase station.
 11. The method of claim 1, wherein the setup messagefurther comprises unit information indicating a unit of data to beswitched to the second base station.
 12. A method of supporting signaltransmission and reception using two or more radio access technologies(RATs), which is supported by a first base station in a firstcommunication network supporting a first RAT, comprising: transmitting asetup message indicating access to a second base station in a secondcommunication network supporting a second RAT to a user equipmentsupporting the two or more RATs; and receiving a completion message forreporting whether the access to the second base station is successful,from the user equipment, wherein if the user equipment successfullyaccesses the second base station redirects data on a specific traffictype among data to be transmitted to the user to the second base stationand data other than the specific traffic type is directly transmitted tothe user equipment.
 13. The method of claim 12, wherein the setupmessage comprises flow information indicating the specific traffic type,which is to be transmitted and received via the second base station. 14.The method of claim 12, wherein the setup message comprises action timeinformation indicating a time of communication between the userequipment and the second base station and wherein the first base stationredirects the data on the specific traffic type to the second basestation on a time indicated by the action time information.
 15. Themethod of claim 12, if the user equipment fails to access the secondbase station, further comprising re-transmitting the setup messageindicating access to a new second base station to the user equipment.16. The method of claim 15, wherein if the completion message is notreceived until a timer, which is started after the setup message istransmitted, expires, the first base station determines that accessestablishment between the user equipment and the second base stationfails.
 17. The method of claim 15, wherein the completion messagecomprises a status value indicating whether the user equipment succeedsin accessing the second base station.
 18. The method of claim 12,wherein the completion message comprises an address value assigned tothe user equipment by the second base station and wherein the first basestation redirects the data on the specific traffic type based on theaddress value.
 19. A user equipment supporting signal transmission andreception using two or more radio access technologies (RATs),comprising: a communication unit; and a processor, the processorconfigured to control the communication unit to receive a setup messageindicating access to a second base station in a second communicationnetwork supporting a second RAT from a first base station in a firstcommunication network supporting a first RAT, the processor configuredto control the communication unit to attempt to access the second basestation, wherein if the access to the second base station issuccessfully performed, data on a specific traffic type is transmittedand received via the second base station and data other than thespecific traffic type are transmitted and received via the first basestation.
 20. A base station in a first communication network supportinga first RAT, which supports signal transmission and reception using twoor more radio access technologies (RATs), comprising: a communicationunit; and a processor, the processor configured to control thecommunication unit to transmit a setup message indicating access to asecond base station in a second communication network supporting asecond RAT to a user equipment supporting the two or more RATs, theprocessor configured to control the communication unit to receive acompletion message for reporting whether the access to the second basestation is successful, from the user equipment, wherein if the userequipment successfully accesses the second base station redirects dataon a specific traffic type among data to be transmitted to the userequipment to the second base station and data other than the specifictraffic type are directly transmitted to the user equipment.